The present invention relates to a method and apparatus for melt spinning man-made filaments and continuously forming the same into a yarn. More particularly, the invention relates to a method and apparatus for making a composite yarn composed of a plurality of yarn components having different physical properties, such as shrinkage or texturizing characteristics.
In present processes involving the melt spinning, drawing, and plying of several yarn components to form a composite yarn, it is recognized that the components may be designed to have different physical properties. For example, it is possible to differently dye the raw polymeric material of the yarn components to produce a spin dyed composite yarn. However, the addition of the dye very often effects the chemical or physical properties of the yarn, and this may result in a disadvantage in that the components of the composite yarn exhibit for example, different strength-elongation properties and different shrinkage properties.
It is an object of the present invention to produce a composite yarn which may be composed of differently dyed yarn components, and with the other properties of the yarn components being related to each other in a desired manner. Thereby, the composite yarn may be prevented from undergoing an undesirable structural change during further processing, or when used, by reason of the different properties of the yarn components.
To produce a textured composite yarn, it is known that the yarn components can be made with different shrinkage properties and plied to form the composite yarn. The composite yarn is then subjected to a heat treatment operation, which results in the shrinkage of at least one of the components which in turn produces a texturizing effect in the composite yarn. Yarn components having different shrinkage properties have previously been prepared from components of a different origin, note for example U.S. Pat. No. 4,019,311, or the components may be from the same origin but drawn at different draw ratios. Producing the yarn components from different origins is disadvantageous, both economically and technically, since it is difficult to prevent the yarn components from having different wearing characteristics. Thus the life of the finished textile product is dependent on the life of the weakest component. Similar disadvantages are present in the production of a composite yarn from yarn components of the same origin but which are drawn at different ratios. Specifically, the drawing influences the denier of the yarn components in a significant manner, so that the components have different deniers. Further, the strength-elongation behavior is affected so that only one yarn component may be considered as a wearing component. If the slightly drawn component shows a greater shrinkage characteristic, this relatively weak component will form the limiting wear component of the composite yarn, i.e., the component which determines the physical properties. As a result, the composite yarn is inferior as far as its physical properties are concerned.
It is according a more specific object of the present invention to produce a composite yarn which can be texturized, and in which the yarn components are of the same origin, are simultaneously spun and drawn, and have the same denier and substantially identical strength-elongation properties, and yet have sufficiently different shrinkage properties to permit the texturizing of the composite yarn.
It is also known that so-called "spun-like" filament yarn can be produced from man-made continuous filaments, by breaking the filaments as part of an overdrawing process. Thus for example, yarn components may first be produced which have different breaking elongations, and these components are then plied and jointly drawn at a given draw ratio which is in the range of the breaking elongation of the component having the lowest breaking elongation properties. Here again however, it is disadvantageous to produce the yarn components from different origins, or to subject the yarn components from the same origin to different draw ratios. It is thus a further object of the present invention to produce a composite yarn wherein the components have the same denier, and also certain other similar physical properties, but wherein the breaking elongation properties of the filaments are different in the yarn components, so that a portion of the filaments can be broken in a subsequent drawing process without damaging the other portion of the filaments.